Panels that are relatively flat and thin tend to be susceptible to transmitting or even generating vibration or noise and it has long been recognized that damping such noise or vibration would be desirable in many applications. For example, considerable attention has been devoted to the development of sound-damping strips or elements that can be inserted between two elements (such as a glass sheet and the metal bodywork of a vehicle) in order to cause acoustic attenuation of the noise propagating through at least one of the elements. See, for example, U.S. published applications 2006/0165977; 2006/0182978; 2008/0056505; and 2007/0284916. However, alternative solutions to the problem of panel vibration or noise generation would be desirable, so as to provide a greater range of options to engineers seeking to design assemblies containing such panels.